include config.h in all sources

After we've been hit by Large File Support problems several times in
the past week (which only occur on 32 bit platforms, which I don't
have), this is yet another attempt to fix the issue.

src/check.h

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_CHECK_H
+#define MPD_CHECK_H
+
+/*
+ * All sources must include config.h on the first line to ensure that
+ * Large File Support is configured properly.  This header checks
+ * whether this has happened.
+ *
+ * Usage: include this header before you use any of the above types.
+ * It will stop the compiler if something went wrong.
+ *
+ * This is Linux/glibc specific, and only enabled in the debug build,
+ * so bugs in this headers don't affect users with production builds.
+ *
+ */
+
+#ifndef PACKAGE_VERSION
+#error config.h missing
+#endif
+
+#if defined(__linux__) && !defined(NDEBUG) && defined(ENABLE_LARGEFILE) && \
+	defined(_FEATURES_H) && defined(__i386__) && \
+	!defined(__USE_FILE_OFFSET64)
+/* on i386, check if LFS is enabled */
+#error config.h was included too late
+#endif
+
+#endif